Best way to learn how to program MCUs?

I'm coming from a background of programming Arduino's and Raspberry Pi's. For this MCU, I'm learning on a FRDM-K64F. I see that I have to initialize what pins I'm using, use libraries created by NXP (some are dated on the MCUXpresso API Reference Manual), etc. I was wondering if there were any courses or lessons that are progressive.

Where I start with the teacher assuming the reader doesn't know anything and brings them up to an acceptable level where we can do what we want.